Baby female Betta fish

Steps

Method 1

1. Wait until characteristics begin to develop with age. Male and female Betta fish will look very similar when young. This is because their body has not yet developed to the point where sexual characteristics are manifested. Wait until you can either see obvious male characteristics or at about two months of age before sexing your Betta.
2. Observe the size and shape of their fins. Male Betta fish will generally have long dorsal (top), ventral (bottom), and caudal (tail) fins. Often 2-3+ times their body height. The dorsal and caudal fins will often droop due to their length. Female Betta fish will typically have shorter fins about as long as the Betta is tall or shorter. Female Betta's ventral fin may often resemble a hair comb.
   • Short fins may indicate female gender, but this characteristic should be combined with other evidence before sexing is conclusive.
3. Note his or her colors. Males typically have bright colors. Females do not. Females tend to have subdued or dull colors, especially in the body. Bright blue, green, and red coloration in the body and fins is a good indication of a male Betta.
   • Colors can change depending on the stress level of the fish. Female Bettas will be more colorful when stressed than non-stressed females.
4. Look for the egg spot. Female Bettas will have a small white spot (the ovipositor tube) on their underside. This spot will resemble a grain of salt. It is located between the near the edge of the ventral fin near the head of the Betta. This is generally a fool-proof method of identifying females-males never have this spot.
   • Finding this spot may be difficult with younger females whose sexual organs have not fully developed. As the fish ages and becomes larger, the ovipositor tube will become larger and easier to see.
   • If you are having trouble viewing the location of the spot, consider feeding or preparing to feed your fish. He or she will likely move to the top and angle himself or herself so you can more easily view the location.
5. Compare their body shapes. Male and female Betta fish have subtle differences in body shape. Males tend to be long and thin. Females tend to be shorter and thicker. This is a subtle difference. You will probably want to familiarize yourself with obviously male Betta fish to use this method to sex Bettas. Female Bettas almost look like stubby males when comparing body shape.
6. Put a mirror beside or in the tank. Bettas will flare at other males. Both male and female Betta fish have aggressive tendencies. However, male are typically more likely to engage in aggressive behavior. When you place a mirror beside or in your Betta's tank, your Betta will see another Betta. Males will likely stretch or flare their gills to show dominance. They may even try to attack the mirror.
   • Female Bettas will sometimes flare to show dominance too. However, they do so with less determination. Males tend to become obsessed with the fact that another male is near them.
   • Do not leave the mirror in the tank for extended periods of time. While seeing your male Betta's aggressive display is fun, this can stress your Betta to the point it affects his or her health. Male Betta's fins, particularly, may start to shorten simply due to experiencing long periods of high stress.